Autonomous electro-optical framing camera system with constant ground resolution, unmanned airborne vehicle therefor, and methods of use

Abstract

An aerial reconnaissance system generates imagery of a scene that meets resolution or field of view objectives automatically and autonomously. In one embodiment, a passive method of automatically calculating range to the target from a sequence of airborne reconnaissance camera images is used. Range information is use for controlling the adjustment of a zoom lens to yield frame-to-frame target imagery that has a desired, e.g., constant, ground resolution or field of view at the center of the image despite rapid and significant aircraft altitude and attitude changes. Image to image digital correlation is used to determine the displacement of the target at the focal plane. Camera frame rate and aircraft INS / GPS information is used to accurately determine the frame to frame distance (baseline). The calculated range to target is then used to drive a zoom lens servo mechanism to the proper focal length to yield the desired resolution or field of view for the next image. The method may be performed based on parameters other than range, such as aircraft height and stand off distance.

Description

This invention relates generally to the art of aerial reconnaissance photography, and more particularly to a reconnaissance camera system having an electro-optical imaging sensor or array with zoom lens capability that automatically and autonomously achieves desired ground resolution or field of view objectives for the reconnaissance mission. The invention also relates to a method of using such a sensor to generate images with desired ground resolution, field of view, or image interpretability objectives regardless of the changes in velocity or height of an aerial reconnaissance vehicle incorporating the sensor. The invention also relates to an unmanned aerial vehicle that incorporates the reconnaissance camera system that operates autonomously to meet reconnaissance mission objectives. The camera system can be pre-programmed to capture high resolution images with desired, e.g., constant, ground resolution, field of view or image interpretability value without any human or operator ...

AI Technical Summary

Benefits of technology

Referring to FIG. 1B, the camera assembly 36 includes an imaging array 32 defining a focal plane FP having a center point CE. The camera assembly 36 also includes a housing 38 and a zoom lens 40 having a focal length F, defining the lens axis LA that passes through the center point CE. Aperture plane AP passes through the aperture of lens 40 perpendicular to the lens axis LA. A shutter 41 is provided to selectively expose the array 32 to radiation from the scene. Typically, the housing 38 is isolated from the aircraft 22 in order to reduce vibration or other high frequency, low amplitude motions. Printed circuit cards 39 incorporate the electronics that support operation of the array 32.

In a preferred embodiment of the invention, the camera system 36 is one that is essentially completely autonomous. In particular, the camera system does not require human involvement to adjust operational parameters of the camera system, such as require human involvement to adjust the focal length of the lens or field of view in response to changes in the aircraft velocity, height, or range to the target, in order to meet mission objectives.

Additionally, the commands for the zoom lens drive system 40 / 42 are based on actual flight parameters (e.g., actual values of velocity, height and range to target), and are not based on assumptions on the flight path of the reconnaissance vehicle. Accordingly, the zoom lens focal length, and resulting resolution and NIIRS values are accurate. The system thus can account for differences in the attitude and altitude of the reconnaissance vehicle between the actual flight values during exposure of the array to the scene and the anticipated values (e.g., range, stand-off distance or height, mission parameters generally determined in advance). Therefore, if the aircraft has to deviate from its flight plan, for example due to the presence of clouds, threatening surface to air defenses, or other conditions, the camera system adapts to the changing conditions while still obtaining imagery that meets the mission requirements. As such, the system is more flexible than a camera system with a fixed focal length lens. Additionally, because the proper focal length settings can be determined autonomously, it provides additional flexibility to the choice of platforms and enables the camera system to implemented in an fully autonomous unmanned aerial vehicle.

Note that in the above UAV embodiment of the invention, the need for a man-in-the-loop up-link to command the zoom lens servo to change the field of view is completely avoided. Thus, the present invention is particularly suitable for high altitude, long endurance reconnaissance missions. The present UAV embodiment of the invention permits such a mission to have the additional advantage of dynamic field of view and resolution adjustments to achieve mission objectives (such as preservation of a particular field of view or resolution objective), through autonomous control of a zoom lens for the camera system. Further, the autonomous control of the zoom lens and resulting improvements in imagery can be obtained in the UAV in a completely passive manner from successive frames of imagery.

Problems solved by technology

In military reconnaissance, it is frequently not sufficient to just provide an image of the target itself, but imagery of the surrounding terrain is required as well.

UAVs have been developed by the United States and other countries for military and civilian purposes and are gaining rapidly in their acceptance as a viable mission platform because of their small size, inexpensive procurement and operating cost, limited or no human risk and in some cases, long endurance.

However, these advantages also place unique restrictions on the payloads that they carry, including the reconnaissance cameras.

However, in the case of high altitude, long endurance UAVs, the man-in-the-loop up-link control is no longer always available.

As such, the patent is not truly an autonomous system and would not be suitable for an autonomous system or an UAV type of environment.

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